1. Field of the Invention
The present invention relates to an optical waveguide for an optical connector, an optical connector using the same, and a method of manufacturing the optical waveguide for an optical connector.
2. Description of the Related Art
In recent years, increases in degree of integration and scale of electronic devices have caused heat generation from and power consumption of electrical interconnect lines used frequently for connection between boards in the devices and between chips on the boards to become problems. An optical interconnection technique has been developed which replaces these electrical interconnect lines with light-weight low-heat-generating flexible polymer optical waveguides.
For such optical interconnection, an optical connector for use in coupling between boards and the like includes a strip-shaped optical waveguide, and a connecting terminal of a predetermined shape known as a ferrule mounted to a longitudinal end portion of the optical waveguide. This optical connector uses a positioning function achieved by the engagement between ferrules placed in opposed relation to provide coupling (optical connection) between an optical fiber and an optical waveguide or between optical waveguides (i.e., between optical connectors), thereby transmitting signals and the like between boards (see, for example, JPCA Standards, “Detail Specification for PMT Connector” JPCA-PE03-01-07S-(2006), Japan Electronics Packaging and Circuits Association, May 2006 (Heisei 18)).
In such an optical connector, an end surface (a connecting end surface) at the distal end of the ferrule at which the longitudinal end surface of the optical waveguide is uncovered is provided with guide holes and the like for insertion of alignment guide pins therein. The connection between optical connectors by the use of ferrules is made in a manner to be described below. Opposite ends of the above-mentioned guide pins are inserted into the guide holes of the ferrules placed so that the above-mentioned connecting end surfaces of the respective ferrules are in face-to-face (or opposed) relation to each other, and the above-mentioned connecting end surfaces are connected in face-to-face abutting relation to each other. This causes the longitudinal end surfaces of the optical fiber and the optical waveguide which are fixed in predetermined positions of the respective ferrules or the longitudinal end surfaces of the respective optical waveguides to abut against each other, thereby establishing an optical connection therebetween.
A typical example of the optical waveguide for use in an optical connector as described above is a strip-shaped optical waveguide having a width of several millimeters and a length in the range of several to tens of centimeters, and including, for example, eight, 12 or 24 cores across the width thereof. Such a strip-shaped optical waveguide having a narrow width is isolated and formed to a predetermined size by cutting a wider elongated film-shaped optical waveguide to a predetermined length, and then cutting the same to a predetermined width along the optical axis of each of the above-mentioned cores by dicing or using a laser beam and the like. The isolated strip-shaped optical waveguide of the predetermined size is inserted into a first insertion opening of an optical waveguide fixing through hole of the above-mentioned ferrule, and is fixed, with a first longitudinal end surface (an optical connection surface) of the strip-shaped optical waveguide revealed from a second exit opening of the through hole provided in the connecting end surface (front surface) of the ferrule having the above-mentioned guide holes (see Japanese Published Patent Application No. 2000-2820 and Japanese Published Patent Application No. 2006-39282).
However, the optical waveguides for an optical connector isolated using dicing as mentioned above have the disadvantage of being low in dimensional accuracy and, in particular, being large in variations in dimensional accuracy across the width of the optical waveguides because of the limited performance of cutting using dicing. Such large variations in size across the width of the optical waveguides cause the optical axes of respective cores in optical waveguides in abutting relation not to coincide with each other, thereby resulting in increased optical coupling losses, even when the optical waveguides are fitted into and fixed in respective optical waveguide fixing through holes formed in a predetermined position of ferrules and the optical connectors are connected in face-to-face abutting relation to each other while being aligned using the guide pins and the like.
The optical waveguides for an optical connector isolated using a laser beam have improved dimensional accuracy across the width thereof as compared with those isolated using the above-mentioned dicing, but cause the decrease in performance of the optical waveguides because of heating by the laser beam. Unlike the dicing, the use of the laser beam has the advantage of being able to isolate an optical waveguide in a curved fashion, but has the disadvantage of requiring an additional step for cleaning for the purpose of removing residues left after machining.
In view of the foregoing, an inexpensive optical waveguide for an optical connector is provided which is accurately positioned across the width of cores when inserted in and fixed in an optical waveguide fixing through hole of a ferrule to provide low optical coupling loss when connected, an optical connector using the same, and a method of manufacturing an optical waveguide for an optical connector.